Alloy steel



Patented July 2, 1940 1 [UNITED STATES ALLOY STEEL Clarence H. Lorig,Columbus, Ohio, assignor to Battelle Memorial Institute, Columbus, Ohio,a

corporation of Ohio No Drawing. Application July 11, 1938, Serial No.218,633

5 Claims.

My invention relates to an alloy steel. It relates more particularly toa steel which has a high sensitivity to work-hardening.

One of the objects of this invention is the provision of arr alloy steelwhich may be used for producing wrought and cast articles having a highcapacity for workhardening.

A further object of this invention is the provision of an alloy steelused for producing artim cles having a high sensitivity towork-hardening that possesses great strength and toughness.

Still another object of this invention is the provision of awork-hardenable alloy steel product having great strength and toughness.

Other objects and-advantages of my invention will become apparent fromthe following description and claims.

I have found that the manganese content of the 11 to 14 per centmanganese work-hardening steel can be substantially reduced by alloyingwith copper and molybdenum and that the stabilization of the austenitestructure of this type of work-hardening steel can be accomplished byemploying much lower manganese contents when both copper and molybdenumare present. The

, 30 traces to 3.0 per cent, the remainder being iron together with theusual amounts of silicon, suliur, and phosphorus normally in steel. Fromtraces up to 0.15 per cent phosphorus, from traces to martensite bycoldworking is rapid.

up to 0.10 per cent sulfur, and from traces up to 1.5 per cent siliconmay be present in the steel. Some chromium may be used to furtherincrease the wear resistance and to raise the yield and tensilestrengths of the steel. For this purpose, however, less than 3 per centof chromium is satisfactory.

I have discovered the combining of manganese, copper, molybdenum, andcarbon in the proportions indicated makes steel very sluggish toallotropic changes, so that in the water-quenched condition or aftercooling quickly in air it stays in the austenitic state. However, thechanges are not too sluggish, so that cold-working will cause theworked'surface of the steel to transform from soft austenite toextremely hard martensite. High sensitivity to work-hardening isobtained when the transformation of austenite In applications where mysteel is subjected to combined pounding or impact and abrasion, thetransformation is rapid and the steel resists wear to a. remarkabledegree. New, hard surfaces form as rapidly as the earlier martensiticsurfaces 25 are removed. by wear.

The following table lists the hardness of a number of steels afterdifierent heat treatments and shows the relative W0rk-hardenability ofthe. steels by the difference in Rockwell C hard- 0 ness of the unworkedsurface and the hardness at the bottom of a Brinell impression where themetal is worked.

- 35 Hardness after various heat treatments 1650" F. water quenched 1650F. air cooled 1650 F. furnace cooled.

0, per Mn, Cu, Mo, 40 Steel N cent percent percen percent Rockwell ORockwell C? Rockwell (7" 40 Brinell Brinell Briuell hardness Sm Bqttomof hardness Bo-ttom' of hardness Si Bottom of face Brinell lm- SurfaceBrlnell ll'Ilface Brinell impression plESSlDIl pressmn 1.25 6. 0 3.0Trace 221 22 38 225 42 404 41 47 1. 7. 0 3. 0 Trace 228 24 40 246 24 46385 38 46 c 1. 25 7. 0 3.0 0.50 229 23 39 229 18 40 378 40 54 1. 25 7.0 1. 5 0. 50 224 18 38 241 18 42 308 i 39 55 1. 25 4. 0 1.0 0. 50 226 20250 21 43 518 49 54 l. 25 i 4.0 2.0 1.00 229 .20 34 232 16 560 52 58 1.3. 0 3. 0 O. 5 269 28 43 354 33 46 499 49 54 1. 00 3. 0 3. 0 0.5 215 2742 205 20 44 518 .50 54 55 0. 75 3. 0 3. 0 0. 5 477 54 435 50 56 514 5254 1.25 5.0 3.0 0.25 224 18 30 234 16 41 141 42 51 quenching in'waterfrom 1900" F. had a Brinell hardness of 1'75, a Rockwell "C hardness of13 on' the unworked surface, and a Rockwell C hardness of 40 on thebottom of a Brinell impression.

' Water-quenched specimens of steel coming within the range ofcomposition which I previously'specified will have-a Brinell hardness inexcess of 210. In the range of composition centering around 1.00 to 1.5per cent carbon, 3 to 7 per cent manganese, 1 to 4 per cent copper, andfrom traces to 1.00 per cent molybdenum, which is my preferredrange,-Brinell hardnesses of water-quenched specimens are from 210 toabout 260, or values that are substantially above the value for the 14per cent manganese steel. The higher hardness is also associated withhigher tensile strength. In this range of preferred composition, thesteeltransforms very rapidly at the surface from soft austenite toextremely hard martensite on cold working, as shown by the difference inRockwell "C" hardness of the unworked surface and of the bottom of theBrinell impression of water-quenched material. The aircooied steel inthe same range of composition is also austenitic and also transforms tomartensite on cold-working. After furnace cooling, the steel ispartially or fully martensitic and hard.

Below the preferred range of carbon and alloy contents, it is moredifficult to obtain the steel in the austenitic state and thus make itwork-hardenable without an extremely drastic quenching from hightemperatures.

- Carbon has a very powerful influence on stabilizing austenite and inmaking the steel suitable for work-hardening. With carboncontents below1.0 per cent, it becomes increasingly dimcult to develop work-hardeningproperties in the steel. A suitable carbon range is quite narrow, as Ihave found that with carbon contents above 1.50 per cent the steel notonlybecomes harder in the quenched state but becomes less satisfactoryfor work-hardening. Carbon is, therefore, an important element whichmust be kept within lclose limits in my steel.

Copper and molybdenum augment carbon and manganese in retainingaust'enite. and molybdenum retard therate of transformation of gammairon to-alpha iron, and particularly so in the presence of manganese andcarbon. Consequently, I have found it possible to reduce the manganesein austenitic work-hardening steel as much as 75 per cent by alloyingwith copper and molybdenum. 1 to 5 per cent copper and from traces to 3per cent molybdenum make possible a reduction in the amount of manganeseof from 1 to 3 times the total percentage of copper and molybdenumadded. Too high a molybdenum content like too high a carbon 'contenttends to harden the steel when waterquenched, making it less susceptibleto workhardening. For that reason, I prefer to limit its use below 3 percent. Excellent results are obtained with 0.25 per cent to 0.50 per centmolybdenum.,

In addition to its influence on stabilizing austenite, copper increasesthe strengthof the steel. In the range of composition in which the steelis machinable, copper also aids the machinability.

An important advantage of my alloysteel over the high-manganese steel isthat in the range of composition of about 2 to 4 per cent of copper,

5 to 7 per cent of manganese, traces to 0.50 per ;wili have fix-lbs.

Both copper high-resistance to the combination of repeated cent ofmolybdenum, and 1.00 to 1.50 per cent of carbon the steel is machinablewith ordinary carbon and high-speed steel tools. The machinability ofthe steel in this range of composition constitutes quite an advance inthe art, as the high-manganese steel can be machined only with 0 M M OMaximubrll Brinell perml-Ss-1 e perperperpermachining cent cent centcent hardness speed,

R. P. M.

l. 25 3. 0 Trace 3. 0 321 167 1. 25 6. 0 Trace 3. 0 406 l. 25 7.0 Trace3.0 380 l. 25 5. 0 Trace 13. 0 415 87 l. 25 2. 0 0.5 3. 0 415 45 Aftermachining, the steel can be made workhardenable by heat-treating andliquid or airquenching.

The higher quenching temperatures up to a certain maximum were found toimprove the ductility of the steel considerably. A quenching temperatureabove 1800 F. was found to be most satisfactory, although it is possibleto quench from lower-temperatures.

Mechanical properties of the steel in the preferred range of compositionare excellent. Its toughness was demonstrated with key-hole notchedCharpy specimens water-quenched and tested for impact in a machine of120 ft.-lb. capacity. The specimens absorbed the full 120 ft.-lb. ofenergy of the machine with a single blow without breaking. Any steelcoming within -the-gauge of composition specified hereinbefore animpactfstrfingth in excess of 30 The alloy steel is suitable forservices requiring blows or impact andabrasion. Articles such as platesfor jaw crushe'rs, ball mill liners, roll shells, dipper teeth,caterpillar shoes, etc., can be made from my alloy.

Having thus described my invention, what I claim is:

1. An alloy steel consisting of 0.50 to 1.7 per cent carbon, 2.0 to 9.0per cent manganese, 1 to 5 per cent copper, traces to 3 per centmolybdenum, traces to 0.15 per cent phosphorus, traces to 0.10 per centsulfur, traces to 1.5 per cent silicon, and the balance substantiallyall iron, said steel being austenitic after quenching from a hightemperature.

2. An alloy steel consisting of 1.00 to 1.5 per cent carbon, 3 to 7 percent manganese, 1 to 4 per cent copper, traces to 1.00 per centmolybdenum, traces to 0.15 per cent phosphorus, traces to 0.10 per centsulfur, traces to 1.5 per cent silicon, and the balance substantiallyall iron.-

3. An alloy steel containing 0.50 to 1.7 per cent carbon, 2.0 to 9.0 percent manganese, 1 to 5 per The following table shows the the balancesubstantially iron, said steel being austenitic and work-hardenableafter quenching from ahigh temperature and having a Brinell hardness inexcess of 210 and an impact strength in excess of 30 ft.-lbs. l

4. An alloy steel containing 1.00 to 1.5 per cent carbon, 3 to 7 percent manganese, 1 to 4 per cent copper, tracesto 1.00 per centmolybdenum, traces to 0.15 per cent phosphorus, traces to 0.10 per centsulfur, traces to 1.5 per cent silicon, and the balance substantiallyiron, said steel being austenitic and work-hardehable after quenchingfrom a high temperature and having a Brinell hardness ranging from 210to 260 and having .an impact strength in excess of 120 ft.-1bs.

5. An alloy steel consisting of 1.00 to 1.5 per cent carbon, 3 to 7 percent manganese, 1 to 4 per cent copper, 0.25 to 0.50 per centmolybdenum, traces to 0.15 per cent phosphorus, traces to 0.10 per centsulfur, traces to 1.5 per cent silicon, and the balance substantiallyall iron.

CLARENCE H. LORIG.

